🔗 Share this article

Among seabirds to polar bears, chimpanzees to orangutans, various animals engage in mouth-to-mouth contact. Currently, researchers propose that ancient hominins did it too – and possibly exchanged kisses with early Homo sapiens.

Common Oral Evidence

This isn't the initial instance experts have proposed ancient relatives and Homo sapiens were intimately acquainted. Among earlier research, scientists have discovered humans and their thick-browed cousins possessed the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Likely they were kissing," she said, explaining that the idea chimed with research that has found people of non-African ancestry have bits of Neanderthal DNA in their genetic makeup, revealing interbreeding was occurring.

Intimate Spin

"This offers a more romantic spin on human-Neanderthal relations," the lead researcher said.

Publishing in the journal a scientific periodical, the researcher and colleagues detail how, to investigate the evolutionary origins of kissing, they first had to develop a description that was not restricted by how humans kiss.

Describing Kissing

"There have been some efforts to describe a kiss, but it's largely focused on humans, which implies that essentially non-human species do not engage in this. Now we understand that they probably do, it may appear different from what human kissing looks like," explained Brindle.

However, she said some actions that resembled kissing were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", seen in aquatic species known as certain marine animals.

As a result the team came up with a description of kissing centered around friendly interactions involving directed oral interaction with a member of the same species, with some motion of the oral area but absence of nutrition.

Research Methods

The lead researcher said they concentrated on accounts of intimate behavior in primates from Africa and Asian regions, including bonobos, chimpanzees and great apes, and used digital recordings to confirm the observations.

The researchers then combined this data with details on the evolutionary relationships between living and extinct species of such primates.

Evolutionary Timeline

Researchers say the findings indicate kissing developed somewhere between 21.5 million and 16.9m years ago in the ancestors of the large apes.

The position of ancient hominins on this family tree suggests it is likely they, too, engaged in a intimate act, the researchers conclude. But the behavior might not have been confined to their specific group.

"Reality that humans engage intimately, the fact that we now have demonstrated that Neanderthals very likely kissed, suggests that the both groups are probably did kissed," Brindle added.

Evolutionary Significance

While the scientific reasoning is debated, Brindle explained intimate contact could be employed in reproductive situations to potentially increase reproductive success or assist in selecting between mates, while it could assist strengthen connections when used in a non-sexual manner.

Another expert in the activities of great apes said that as intimate contact was seen in a wide range of primates it made sense its roots lie deep in our ancient history, and an examination of different forms of kissing among a broader range of animals might extend its beginnings back even earlier still.

"Behaviors that we think of as characteristics of our species, like kissing, are not exclusive to us if we examine carefully at different species," he said.

Cultural Elements

An archaeology expert said that kissing had a social component as it was not universal to all societies.

"Nonetheless, as people we thrive or fail on the quality of our emotional bonds, and methods of promoting trust and intimacy will have been important for millions of years," she said. "It might be an concept that seems a bit contradictory to our misplaced ideas of a supposedly aggressive and ancient history, but actually it should be expected that Neanderthals – and even them and our own species together – engaged intimately."